Java vs C++: The Most Important Differences

In this post, we feature a comprehensive article about Java vs C++ and their most important differences. Java and C++ are the object-oriented programming languages. C++ is platform dependent and Java is platform independent language. In this tutorial, we see the features of Java and C++ to see the differences.

1. Overview

We look at the comparison of Java vs C++ languages in this article. They can be used for developing software and executing the code. Java code is converted into bytecode after compilation. The java interpreter runs the bytecode and the output is created. C++ has a specific compiler for an operating system. C++ code is converted into machine level language. A binary file is created and executed for creating the output in C++.

2. Java vs C++

2.1 Prerequisites

Java 8 is required on the linux, windows or mac operating system. Eclipse Oxygen can be used for this example. Eclipse C++ is necessary on the operating system which you want to execute the code.

2.2 Download

You can download Java 8 from the Oracle web site . Eclipse Oxygen can be downloaded from the eclipse web site. Eclipse C++ is available at this link.

2.3 Setup

2.3.1 Java Setup

Below is the setup commands required for the Java Environment.

Java Setup

JAVA_HOME=”/jboss/jdk1.8.0_73″
export JAVA_HOME
PATH=$JAVA_HOME/bin:$PATH
export PATH

2.3.2 C++ Setup

Eclipse C++ installation sets the environment for C++ development and project building.

2.4 IDE

2.4.1 Eclipse Oxygen Setup

The ‘eclipse-java-oxygen-2-macosx-cocoa-x86_64.tar’ can be downloaded from the eclipse website. The tar file is opened by double click. The tar file is unzipped by using the archive utility. After unzipping, you will find the eclipse icon in the folder. You can move the eclipse icon from the folder to applications by dragging the icon.

2.4.2 Eclipse C++ Setup

The ‘eclipse-cpp-2019-06-R-macosx-cocoa-x86_64.dmg’ can be downloaded from the eclipse C/C++ website. After installing the application on macos, you will find the eclipse icon in the folder. You can move the eclipse icon from the folder to applications by dragging the icon.

2.5 Launching IDE

2.5.1 Eclipse Java

Eclipse has features related to language support, customization, and extension. You can click on the eclipse icon to launch eclipse. The eclipse screen pops up as shown in the screen shot below:

You can select the workspace from the screen which pops up. The attached image shows how it can be selected.

You can see the eclipse workbench on the screen. The attached screen shot shows the Eclipse project screen.

Java Hello World class prints the greetings. The screenshot below is added to show the class and execution on eclipse.

2.5.1 Eclipse C++

C++ code is created to print “Hello World” and executed on Eclipse C++. The screen shot below shows the Hello World in C++ and the printed output.

2.6 Memory Management

Java language has features related to memory management and it is a memory safe language. Garbage collection is a feature which helps in collecting the resources which are free and released. C++ allows dynamic memory allocation which causes problems due to developer defects. Developer in java cannot go beyond the allocated memory, whereas in C++, developer can access beyond the allocated memory. In java, it throws an error and C++ allows the access which leads to defects in the code.

2.7 Exceptional Handling

In Java, exception handling is possible by using try, catch and finally blocks. C++ language has features for try and catch to handle the exceptions. In java, exception classes can be extended and created for various errors. In C++, standard library has exceptions which need to be derived for handling various errors. If a method throws an exception in Java, try and catch has to be created to handle the exception while invoking the method. In C++, the invoking can exclude the try and catch block.

2.8 Multiple Inheritance

Multiple inheritance is supported in C++. Let us take an example to see how it is handled in Java and C++. Truck is an vehicle and a machine.

Java does not support multiple inheritance. Each class is able to extend only on one class but is able to implement more than one interfaces. The sample code shows below Truck class implementing interfaces Machine and Vehicle.

Interfaces

public interface Machine
{
    int  velocity=50;
    public int getDistance();
}
public interface Vehicle
{
    int distanceTravelled=100;
    public int getVelocity();
}
public class Truck implements Machine, Vehicle
{
    int time;
    int velocity;
    int distanceTravelled;
    
    
    public Truck(int velocity, int time)
    {
        this.velocity = velocity;
        this.time = time;
    }
    
    public int getDistance()
    {
        distanceTravelled= velocity*time; 
        System.out.println("Total Distance  is : "+distanceTravelled);
    }
    public int getVelocity()
    {
        int velocity=distanceTravelled/time;
        System.out.println("Velocity  is : "+ velocity);
    }
    public static void main(String args[])
    {
        Truck truck = new Truck(50,2);
        truck.getDistance();
        truck.getVelocity();
    }
}

In C++, multiple inheritance is a feature where you can inherit multiple classes. The constructors of the classes inherited are invoked in the order of inheritance. In the example below, Machine will be called before the Vehicle when Truck object is instantiated.

C++ Inheritance

#include 
using namespace std; 
  
class Vehicle
{ 
public: 
  Vehicle()  { cout << "Vehicle's constructor is invoked" << endl; } 
}; 
  
class Machine 
{ 
public: 
  Machine()  { cout << "Machine's constructor is invoked " << endl; } 
}; 
  
class Truck: public Machine, public Vehicle  
{ 
public: 
  Truck()  { cout << "Truck's constructor is invoked " << endl; } 
}; 
  
int main() 
{ 
    Truck truck; 
    return 0; 
}

2.9 Threads

Java has in built classes to create threads. To create a new thread, a class has to extend a Thread class and the run method has to be overridden. In C++, commercial libraries are provided for thread support till C++11.

Java Threads

public class NewThread extends Thread
{  
  public void run()
  {  
    System.out.println("Thread running now");  
  }
  
  public static void main(String args[])
  {  
    NewThread newThread =new NewThread();  
    newThread.start();  
  }  
}

Java provides another way to create Threads. A class which implements Runnable can be instantiated and passed as a parameter to the Thread class. Sample code is provided below:

Java Thread Object

public class ThreadObject implements Runnable
{  
  public void run()
  {  
    System.out.println("ThreadObject running");  
  }  
  
public static void main(String args[])
{  
  ThreadObject threadObject =new ThreadObject();  
  Thread thread =new Thread(threadObject);  
  thread.start();  
 }  
}

C++11 has a thread class. A developer can create a new thread object. The callable method can be passed as constructor’s argument. A thread is started when the thread object is instantiated.The code sample below shows how to create threads using function pointer, lambda expression and function object.

Threading in C++

#include  
#include  
using namespace std; 
  
void invoke_method(int Z) 
{ 
    for (int i = 0; i < Z; i++) { 
        cout << "Thread - function pointer as callable method\n"; 
    } 
} 
  
class thread_object { 
public: 
    void operator()(int x) 
    { 
        for (int i = 0; i < x; i++) 
            cout << "Thread - function object as  callable\n"; 
    } 
}; 
  
int main() 
{ 
    cout << "Threads 1 and 2 and 3 and 4 "
         "operating independently" << endl; 
  
    thread thre1(foo, 4); 
  
    thread thre2(thread_object(), 4); 
  
    auto g = [](int x) { 
        for (int i = 0; i < x; i++) 
            cout << "Thread - lambda expression as callable\n"; 
    }; 
  
    thread thre3(g, 4);
    
    thread thre4(foo,4)
  
    thre1.join(); 
  
    thre2.join(); 
  
    thre3.join(); 
    
    thre4.join();
  
    return 0; 
}

2.10 Portability

Java language is interpreted by the java interpreter on the computer independent of the operating system. C++ code needs to be compiled by the compiler specific to the operating system.

C++ code needs to be compiled, linked and loaded by the operating system specific versions. Preprocessing of the code is also operating system specific.

2.11 Types

Java language has primitive and object types. Java has features related to autoboxing which converts the types automatically. The java.lang.Object class is the base class for all the classes and Java follows the single root chain of command. In C++, single root chain of command is not there.

C++ data types are categorized as primitive, derived and user defined. The derived data types are array, pointer and reference. User defined data types are struct, union, class and enumeration.

2.12 Libraries

Java packages help in packaging classes. Package scope is another feature in Java language. Java archives help in grouping the package of classes for execution and installation purposes.

C++ libraries are code packages and they can be static or dynamic. C++ library has a header and a precompiled binaries. C++ library is packaged with binaries, static libraries, shared libraries and resources.

2.13 Runtime Errors

In java, runtime errors are presented by the compiler and the interpreter. In C++, developer takes care of the runtime errors by programmatically checking and validating the code.

2.14 Documentation

Java has feature to support comments which can be used for documentation generator. In C++, documentation can be generated using Doxygen from the comment blocks.

2.15 Mobile & Web & Desktop

Java language can be used for mobile, web and desktop application development. C++ can also be used for mobile and desktop native applications. ISAPI and C++ web based applications are popular on microsoft stack.

3. Conclusion

Overall, Java has great benefits over C++. The comparison table below captures the differences between Java and C++.

Comparison Table

4. Download the Source Code

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